The production of sand particles in oil wells can result in severe problems with regard to erosion in valves or bends as well as possible collapse of the reservoir, and filling up of separators. This paper will discuss the erosion based sand monitoring system, and how this has helped field operators across the world to operate within optimized, but safe production limits to avoid these problems. The system has operational experience from the last seven years from both topside and subsea completed wells, and field data from these installations will be given. The paper will also present data from different laboratory tests. Finally, the latest erosion correlation model developed together with a major Norwegian oil company will be discussed. This model gives the correlation between the probe erosion and other critical components in the system, e.g. bends.
The production of sand and solids in oil and gas can represent a major problem in terms of erosion damage. Sand production can also lead to a degradation, or in the worst case, a collapse of the reservoir. Unexpected breakdown of the reservoir and water breakthrough can occur, resulting in increased sand content of the well fluid. Process equipment could also fill up due to the settling of sand. In addition to the safety and production technical aspects of unwanted/uncontrolled sand production, the active use of proper on-line sand monitoring equipment will also have a cost reducing impact since piping tolerances with respect to erosion may be reduced.
Sand control has in the past been sought mainly through downhole techniques like screens/gravel packs.
A gravel pack will, however, limit the production capacity from the reservoir, and it has also been seen to fail with drastic consequences. In addition, the cost of a gravel pack operation can make it desirable to seek other solutions. The system presented in this article allows continuous monitoring of the status of sand production and erosion in any type of well, and will serve both as a safety device, and as a tool for optimizing and controlling the oil/gas production. An on- line sand monitoring system can also lower capital expenditures by reducing the production system tolerance with respect to erosion. During testing before a well is put into normal production, and at later stages, maximum sand free rate (MSFR) tests with on line sand monitoring can be performed to establish the maximum acceptable production rates. However, downhole conditions can change over time resulting in sand production. This leads to a requirement for continuous sand monitoring.
This paper describes experience from use of an erosion based sand monitoring system. The erosion rates read directly from the probe elements can, using direct correlations, be used to quantify the erosion in the piping system itself. Predicting erosion in other critical components in the line can be equally important from a safety point of view. The system does not need any on site calibration (injection of known quantities of sand) to quantify sand contents, and can be used equally well in all flow regimes, single or multiphase, and it has no lower threshold for the smallest detectable sand concentration
SAND PROBE SYSTEM DESCRIPTION
This sand monitoring system is based on a probe that detects sand production through erosion of sensing elements directly exposed to the media. When sand transported by the media hits the probe, the sensing elements will be eroded and the resulting increase in resistance can be continuously measured, and the thickness reduction of the elements can then be easily quantified. Each element is connected to electrical wires and fed with a constant current. By m
